Por Juliana Americo

The construction of our metal catcher OGM

We needed a feasible way to produce and apply MTαβ4 in industry and, with that in mind, we decided to introduce MTαβ4 gene in a special bacteria, Cupriavidus metallidurans. This bacteria naturally survives in very harsh conditions, as in the presence of high amounts of heavy metals and it would work both as a biofactory and a carrying particle for MTαβ4. One additional useful feature of C. metallidurans is its metabolic versatility: it can feed from many different compounds and it can even grow in the absence of any organic substance. This means we would have a wide range of possibilities to find the biomass production conditions with the best yield and cost benefits.

The idea was to make the bacteria produce the metal-binding protein MTαβ4 in its outer surface. The result would be a bacteria coated by MTαβ4 which could directly interact and capture metals from its surroundings. To achieve this, we made some improvements in MTαβ4 gene. One of which was to connect MTαβ4 to an auto-transporter protein, which is able to move though the bacterial membrane and anchor itself in its outer surface. We put this new gene together by means of DNA synthesis and genetic engineering and, then, we used a plasmid, a synthetic small circular DNA molecule, to delivery this new gene to C. metallidurans. It may sound complicated, but it is very simple: the gene is like an instruction manual, we just adapted its language and message in a way bacteria could read and follow to produce the MTαβ4 exactly in the location we wanted!

OGM plasmid

We verified if C. metallidurans was able to “read” the introduced gene and produce MTαβ4 in its outer surface, like we planned. We took bacterial cells under an electronic microscopy, making use of an antibody which specifically recognize the MTαβ4 protein, to check either the protein was there and where. This image was made of a very thin slice of bacteria, but still we can see several antibody marks (black dots indicated by arrows), showing the presence of MTαβ4 in the bacteria surface (and in its way up there!).

microscopy etag